The present invention relates to a dental handpiece with supply lines running axially inside a longitudinal handpiece jacket. The handpiece jacket and the supply lines are divided transversely to form several handpiece sections and each of one of the two ends of two adjacent handpiece sections have an axially projecting sleeve in which the end of the other handpiece section can be inserted; the two ends for the detachable connection of the adjacent handpiece sections are provided with a screw thread each, either as inside thread of the projecting sleeve forming a pipe connection-like threaded portion of one handpiece section, or as outside thread of the handpiece sleeve also forming a pipe stub like threaded portion of the end inserted in the sleeve of the other handpiece section. In order to supply the inside of such a handpiece, e.g., bearing parts or rotating parts with oil or another lubricant, the above screw connection is disconnected so that the lubricant can be introduced from the partition portion into the corresponding handpiece section. Such lubrication is performed several times a day.
Such a dental handpiece is known from German Patent 11 16 860. With this known handpiece, the screwing and unscrewing of the adjacent handpiece sections, because of the many threads required by a sufficiently stable connection of the handpiece sections, requires much time. It has been found that because of the great time consumption, lubrication of the handpieces is frequently neglected so that they are damaged.
From the German Laid Open Document 23 59 506 it is known how to connect a quick-connection unit fixedly to the screw threads at the end of the two adjacent handpiece sections. The quick-connection comprises a bayonet catch and involves relatively high cost. The advantage of quick actuation is negated by the high cost.
Finally, the Swiss Patent No. 354,893 shows a similar dental handpiece, where the ends of the adjacent handpiece sections have no threads. The end, to be inserted in the sleeve of one handpiece section, and of the other handpiece section, has an external torus which during the connection of adjacent handpiece sections engages an internal annular groove of the elastic sleeve. After effecting this engagement, a locking sleeve must be slid from the handpiece section having the sleeve in the axial direction over the elastic sleeve. Aside from the fact that the insertion of the handpiece section with the torus into the elastic sleeve and the sliding over of the locking sleeve is difficult and time consuming, a tight connection of the supply lines of the two adjacent handpiece sections cannot be achieved.
Accordingly, it is an object of the present invention to provide a dental handpiece of the type described initially, where the screw threads of two adjacent handpiece sections can be connected and disconnected quickly and safely, avoiding much cost, while simultaneously ensuring tight connection of the supply lines of the two adjacent handpiece sections.
Another object of the present invention is to provide a dental handpiece of the foregoing character which may be economically fabricated and easily maintained in service.
A further object of the present invention is to provide a dental handpiece, as described, which has a substantially long operating life.